The updated BOSZ synthetic stellar spectral library^★

¹ ELTE Eötvös Loránd University, Gothard Astrophysical Observatory, Szent Imre H. st. 112, 9700 Szombathely, Hungary
e-mail: meszi@gothard.hu
² MTA-ELTE Lendület “Momentum” Milky Way Research Group, Szent Imre h. u. 112., 9700 Szombathely, Hungary
³ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁴ Instituto de Astrofísica de Canarias (IAC), 38200 La Laguna, Tenerife, Spain
⁵ Departamento de Astrofísica, Universidad de La Laguna (ULL), 38206 la Laguna, Tenerife, Spain
⁶ Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences (CSFK), Konkoly Thege M. út 15–17, 1121 Budapest, Hungary
⁷ CSFK, MTA Centre of Excellence, Konkoly Thege Miklós út 15–17, 1121 Budapest, Hungary
⁸ HUN-REN–ELTE Exoplanet Systems Research Group, Szent Imre h. u. 112., 9700 Szombathely, Hungary
⁹ Sensor Science Division, National Institute of Standards and Technology, Gaithersburg, MD 20899-8441, USA
¹⁰ The University of Arizona, Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85719, USA
¹¹ Department of Experimental Physics, Institute of Physics, University of Szeged, Dóm tér 9, 6720 Szeged, Hungary

Received: 22 January 2024
Accepted: 24 June 2024

Abstract

Context. The modeling of stellar spectra of flux standards observed by the Hubble and James Webb space telescopes requires a large synthetic spectral library that covers a wide atmospheric parameter range.

Aims. The aim of this paper is to present and describe the calculation methods behind the updated version of the BOSZ synthetic spectral database, which was originally designed to fit the CALSPEC flux standards. These new local thermodynamic equilibrium (LTE) models incorporate both MARCS and ATLAS9 model atmospheres, updated continuous opacities, and 23 new molecular line lists.

Methods. The new grid was calculated with Synspec using the LTE approximation and covers metallicities [M/H] from −2.5 to 0.75 dex, [α/M] from −0.25 to 0.5 dex, and [C/M] from −0.75 to 0.5 dex, providing spectra for 336 unique compositions. Calculations for stars between 2800 and 8000 K use MARCS model atmospheres, and ATLAS9 is used between 7500 and 16 000 K.

Results. The new BOSZ grid includes 628 620 synthetic spectra from 50 nm to 32 µm with models for 495 T_eff−log 𝑔 parameter pairs per composition and per microturbulent velocity. Each spectrum has eight different resolutions spanning a range from R = 500 to 50 000 as well as the original resolution of the synthesis. The microturbulent velocities are 0, 1, 2, and 4 km s⁻¹.

Conclusions. The new BOSZ grid extends the temperature range to cooler temperatures compared to the original grid because the updated molecular line lists make modeling possible for cooler stars. A publicly available and consistently calculated database of model spectra is important for many astrophysical analyses, for example spectroscopic surveys and the determination of stellar elemental compositions.